Final answer:
A chemoautotroph is an organism that can occupy the first trophic level of a food chain and produce its own food from inorganic molecules, without the need for sunlight.
Step-by-step explanation:
The type of organism that can occupy the first trophic level in a food chain but not perform photosynthesis is known as a chemoautotroph. Unlike photoautotrophs like plants, chemoautotrophs are capable of synthesizing their own food using energy from inorganic molecules instead of relying on sunlight. Chemoautotrophs are often found in environments where sunlight is not available, such as deep-sea hydrothermal vents, and play a crucial role in sustaining the food web in these ecosystems.